The invention describes an apparatus for cathode sputtering for the production of thin coatings on a substrate by means of a plasma in a vacuum processing chamber, consisting essentially of magnets, pole shoes, an anode, a target configured as a cathode of the material to be sputtered, and a masking system.
For the production of thin coatings on a substrate, especially for coating compact disks, many different solutions are known in the state of the art.
For example, EP 0 163 445 describes a target set for an apparatus for vacuum sputtering, having a first and second cathode element of sputtering material, the second surrounding the first. The geometries of the first and second element are such that, when they are in the vacuum, material can be sputtered from the emitting surface of the second element, which surface lies outside that of the first element. The first target element is a ring-shaped cathode and the initial emitting surface of the second element is frustoconical.
U.S. Pat No. 4,747,926, also discloses a frustoconical target for use in a magnetron sputtering apparatus. A one-piece target is fixed to a backing plate and has two surface areas which run parallel to the central region of a planar substrate, and a third inclined area which joins the first and second areas. A magnetic field produces two plasmas of different diameters.
U.S. Pat. No. 4,933,064 discloses a sputtering cathode on the magnetron principle, with a target having at least two concentric projections whose wall surfaces are perpendicular to the sputtering surface. A permanent magnet system has soft-magnetic pole shoes, from whose pole faces magnetic lines of force pass through the projections and cross the sputtering surface.
The described prior art apparatus have several disadvantages. First, they require a relatively high electrical power for supplying the sputtering current. Second, they achieve an unsatisfactory sputtering efficiency, i.e., too much target material is deposited on shielding and masks instead of on the substrate. Third, the mechanical structure of the cathode is too complicated. Fourth, the sputtering current supply (SSV) is prone to arcing, and consequently the SSV frequently shuts down.